CN113556488A

CN113556488A - Signal acquisition method and signal acquisition circuit of image sensor

Info

Publication number: CN113556488A
Application number: CN202010341404.2A
Authority: CN
Inventors: 凌严; 朱虹
Original assignee: Shanghai Oxi Technology Co Ltd
Current assignee: Shanghai Oxi Technology Co Ltd
Priority date: 2020-04-26
Filing date: 2020-04-26
Publication date: 2021-10-26

Abstract

A signal acquisition method of an image sensor and a signal acquisition circuit thereof are provided, wherein the signal acquisition method comprises the following steps: in each signal acquisition period, controlling the potential of the data line to be a target potential so as to apply bias voltage to the photosensitive device of each pixel which is turned on; the signal acquisition period comprises at least one reset frame, and the target potential is a reset potential during the reset frame so as to apply forward bias to the photosensitive device. The signal acquisition method and the signal acquisition circuit can effectively shorten the signal acquisition period, improve the image acquisition speed, and eliminate the influence of historical illumination, ambient light and the device difference of each photosensitive device on residual charge.

Description

Signal acquisition method and signal acquisition circuit of image sensor

Technical Field

The invention relates to the technical field of image sensors, in particular to a signal acquisition method and a signal acquisition circuit of an image sensor.

Background

An image sensor (image sensor) is a sensor device that converts a light image on a photosensitive surface into an electrical signal proportional to the light image by using a photoelectric conversion function of a photosensitive device.

Taking an optical fingerprint sensor as an example, the optical fingerprint sensor is generally composed of a pixel array, control lines (also referred to as drive lines), scanning lines (also referred to as signal readout lines), and the like. Each pixel in the pixel array is provided with a photosensitive device to realize conversion from an optical signal to an electric signal.

A conventional Photo Diode (Photo-Diode) is generally used as a Photo sensor, but due to the influence of various factors such as dark current of the Photo Diode itself and ambient light of an environment where the image sensor is located, before signal acquisition is performed by using the image sensor, useless charges exist on each pixel. Therefore, before signal acquisition is actually performed, it is necessary to perform an emptying process for each pixel of the image sensor.

The existing signal acquisition method needs to be improved in the method of clearing pixels.

Disclosure of Invention

The invention aims to provide a signal acquisition method of an image sensor and a signal acquisition circuit thereof, so as to further improve the signal acquisition speed on the premise of ensuring the emptying effect.

In order to solve the above problem, the present invention provides a signal acquisition method of an image sensor, the image sensor including: a plurality of pixels arranged in an array, a plurality of data lines and a plurality of scan lines, each of the pixels including a light sensing device and a signal switching device, one end of each of the light sensing devices being coupled to one of the data lines through the signal switching device, each of the pixels being connected to one of the scan lines through the signal switching device, the scan lines being adapted to turn on the signal switching devices of the connected pixels line by line, the signal acquisition method comprising: in each signal acquisition period, controlling the potential of the data line to be a target potential so as to apply bias voltage to the photosensitive device of each pixel which is turned on; the signal acquisition period comprises at least one reset frame, and the target potential is a reset potential during the reset frame so as to apply forward bias to the photosensitive device.

Optionally, the step of controlling the potential of the data line to a target potential to apply a bias voltage to the light sensing device of each of the turned-on pixels includes: controlling the other end of the data line to be coupled to the target potential; the signal switching devices of the pixels are turned on row by row, and a bias voltage is applied to the light sensing devices of the turned-on pixels through the data lines.

Optionally, the step of controlling the other end of the data line to be coupled to the target potential includes: controlling the other ends of the plurality of data lines to be coupled to the target potential one by one; or controlling the other ends of the plurality of data lines to be coupled to the target potential at the same time; or controlling the other ends of the plurality of data lines to be coupled to the target potential in groups.

Optionally, before controlling the other end of the data line to be coupled to the target potential, controlling the potential of the data line to be at the target potential to apply a bias voltage to the light sensing device of each of the turned-on pixels further includes: the coupling of the data line to the non-target potential is cut off.

Optionally, the step of disconnecting the coupling of the data line and the non-target potential includes: cutting off the coupling of the plurality of data lines with the non-target potential one by one; or, the coupling of the plurality of data lines with the non-target potential is simultaneously cut off; alternatively, the coupling group of the plurality of data lines and the non-target potential is cut off.

Optionally, for the same data line, after the data line is disconnected from the coupling with the non-target potential, the other end of the data line is controlled to be coupled with the target potential.

Optionally, after the other ends of the data lines are all coupled to the target potential, the signal switching devices of the pixels are turned on line by line, and a bias voltage is applied to the turned-on photosensitive devices of the pixels through the data lines.

Optionally, in the plurality of pixels arranged in an array, the signal switching device of each row of the pixels is coupled to the same scanning line.

Optionally, the signal acquisition cycle further includes: a signal readout frame chronologically positioned after the reset frame, during which the data line is coupled to a data processing channel, the target potential being a readout potential to apply a reverse bias to the photosensitive device.

Optionally, the signal acquisition cycle further includes: and an initialization frame which is located between the at least one reset frame and the signal readout frame and is adjacent to the signal readout frame in time sequence, wherein during the initialization frame, the data line is coupled with a data processing channel, and the target potential is a readout potential to apply a reverse bias to the photosensitive device.

Optionally, the signal acquisition cycle further includes: and at least one clear frame, which is located between the at least one reset frame and the initialization frame in time sequence, wherein during the clear frame, the target potential is a clear potential to apply a reverse bias to the photosensitive device.

Optionally, in the same signal acquisition period, the blanking potentials in different blanking frames are equal or unequal.

Optionally, the at least one clearing frame includes at least one first clearing frame and at least one second clearing frame, and an absolute value of a clearing potential during the first clearing frame proceeding period is greater than an absolute value of a clearing potential during the second clearing frame proceeding period.

Optionally, in the same signal acquisition period, the at least one first clear frame is located before the at least one second clear frame in time sequence.

Optionally, an absolute value of the blanking potential during the first blanking frame proceeding period is 1 to 3 times an absolute value of the blanking potential during the second blanking frame proceeding period.

Optionally, an absolute value of the clear potential is greater than or equal to an absolute value of the readout potential.

Optionally, the other end of each of the photosensitive devices is coupled to a common electrode, and the potential of the common electrode is kept unchanged in each signal acquisition period.

Correspondingly, the present invention also provides a signal acquisition circuit of an image sensor, the image sensor comprising: a plurality of pixels arranged in an array, a plurality of data lines and a plurality of scan lines, each of the pixels including a light sensing device and a signal switching device, one end of each of the light sensing devices being coupled to one of the data lines through the signal switching device, each of the pixels being connected to one of the scan lines through the signal switching device, the scan lines being adapted to turn on the signal switching devices of the connected pixels; the signal acquisition circuit includes: the scanning line control unit is coupled with the plurality of scanning lines, and in each signal acquisition period, the scanning line control unit controls the signal switching devices of the pixels connected with the scanning lines to be turned on line by line through the scanning lines; the signal readout unit is coupled with the data lines and reads the electric signals of the started pixels through the data lines in each signal acquisition period; the signal acquisition circuit further comprises: and a bias control unit coupled to the data line, the bias control unit adapted to control a potential of the data line to a target potential using the signal acquisition method of the present invention during each signal acquisition period to apply a bias to the photosensitive device of each of the pixels that are turned on line by line.

Optionally, the bias control unit includes: and one end of the controller is coupled with the data line, the other end of the controller is coupled with the target potential, and the controller is suitable for controlling the connection and disconnection between the data line and the target potential.

Optionally, the bias control unit further includes: and one end of the restorer is coupled with the data line, the other end of the restorer is coupled with the data processing channel, and the restorer is suitable for controlling the connection and disconnection of the data line and the data processing channel.

Optionally, the controller includes a plurality of data line switches, one end of each data line switch is coupled to one of the data lines, the other end of each data line switch is coupled to a target potential, and the data line switch is adapted to control the connection and disconnection of the corresponding data line coupled to the target potential; the restorer comprises a plurality of restoring switches, one end of each restoring switch is coupled with one data line, the other end of each restoring switch is coupled with a data processing channel corresponding to the connected data line, and the restoring switches are suitable for controlling the connection and disconnection of the data lines and the data processing channels.

Optionally, the bias control unit further includes: a converter adapted to effect conversion of the coupling of the other end of the controller between different target potentials.

Optionally, the signal acquisition cycle includes: at least one reset frame, during the reset frame, the target potential is a reset potential to apply a forward bias to the photosensitive device; a signal readout frame chronologically positioned after the reset frame, during which the data line is coupled to a data processing channel, the target potential being a readout potential to apply a reverse bias to the photosensitive device; an initialization frame positioned between and adjacent to the at least one reset frame and the signal readout frame in time sequence, during which the data lines are coupled to a data processing channel and the target potential is a readout potential to apply a reverse bias to the photosensitive device; at least one clearing frame, wherein the clearing frame is positioned between the reset frame and the initialization frame in time sequence, and the target potential is a clearing potential during the clearing frame to apply a reverse bias voltage to the photosensitive device; the converter includes: a first transfer switch, one end of which is coupled to the other end of the controller, the other end of which is coupled to the reset potential, the first transfer switch being adapted to control the connection and disconnection of the other end of the controller coupled to the reset potential; and each second change-over switch is suitable for controlling the connection and disconnection of the other end of the controller and one clearing potential.

Optionally, the signal acquisition cycle includes: at least one reset frame, during the reset frame, the target potential is a reset potential to apply a forward bias to the photosensitive device; a signal readout frame chronologically positioned after the reset frame, during which the data line is coupled to a data processing channel, the target potential being a readout potential to apply a reverse bias to the photosensitive device; an initialization frame positioned between and adjacent to the at least one reset frame and the signal readout frame in time sequence, during which the data lines are coupled to a data processing channel and the target potential is a readout potential to apply a reverse bias to the photosensitive device; at least one clearing frame, wherein the clearing frame is positioned between the reset frame and the initialization frame in time sequence, and the target potential is a clearing potential during the clearing frame to apply a reverse bias voltage to the photosensitive device; the minimum value of the absolute value of the clear potential is equal to the absolute value of the readout potential; the at least one clear frame includes at least one first clear frame during which an absolute value of a clear potential is greater than a minimum value of the absolute value of the clear potential; the converter includes: a first transfer switch, one end of which is coupled to the other end of the controller, the other end of which is coupled to the reset potential, the first transfer switch being adapted to control the connection and disconnection of the other end of the controller coupled to the reset potential; at least one second transfer switch, one end of the second transfer switch being coupled to the other end of the controller, the other end of the second transfer switch being coupled to a blanking potential during a first blanking frame, the second transfer switch being adapted to control the turning on and off of the coupling of the other end of the controller to a blanking potential during a first blanking frame.

Compared with the prior art, the technical scheme of the invention has the following advantages:

in the signal acquisition method and the signal acquisition circuit provided by the invention, in each signal acquisition period, the plurality of pixels are subjected to signal acquisition, and the potential of the data line is controlled to be a target potential so as to apply bias voltage to the photosensitive device of each turned-on pixel. When the potential of the data line is changed, the load of the data line is only the parasitic capacitance of the data line, so that the load of the data line is small when the potential of the data line is changed, the charge impact is small, the stabilization time required by changing the potential of the data line is short, and the potential change speed of the data line is high, so that the signal acquisition period can be effectively shortened, and the image acquisition speed is improved; and each signal acquisition cycle comprises: the signal acquisition period comprises at least one reset frame, and during the reset frame, the target potential is a reset potential so as to apply forward bias to the photosensitive device; and during the reset frame, applying forward bias to the photosensitive devices, which can be equivalent to irradiating each photosensitive device with strong light, adjusting the initial state of each photosensitive device to be consistent through the reset frame, and eliminating the influence of historical illumination, ambient light and the device difference of each photosensitive device on residual charge.

In an alternative aspect of the present invention, the signal acquisition period further includes: an initialization frame positioned between the at least one reset frame and the signal readout frame and adjacent to the signal readout frame, the data lines coupled to the data processing channels to apply a reverse bias to the photosensitive devices during the initialization frame. During the initialization frame, the data line is coupled with the data processing channel, and the photosensitive device is applied with reverse bias voltage, so that the charge of each turned-on pixel through the data processing channel can be cleared, and the initialization of the pixel is realized; and the initialization frame and the signal readout frame are arranged adjacent in time sequence, and the coupling relation of the data lines is not changed from the initialization frame to the signal readout frame, so that the circuit noise can be effectively inhibited.

In an alternative aspect of the present invention, the signal acquisition period further includes at least one blanking frame, and in each of the blanking frames, the target potential is a blanking potential to apply a reverse bias to the photosensitive device. The emptying frame ensures that the charges generated by each photosensitive device in the reset frame can be effectively emptied. Therefore, through the matching of the reset frame and the empty frame, the image acquisition precision of the image sensor can be improved, and the accuracy of the image acquired each time is ensured; and by controlling the potential change of the data line, forward bias or reverse bias is applied, the load of the data line is small, the potential change speed is high, the reset speed and the emptying speed can be effectively improved, the signal acquisition period can be shortened, and the imaging speed can be improved.

In an alternative aspect of the present invention, the at least one clearing frame includes at least one first clearing frame and at least one second clearing frame, wherein an absolute value of a clearing potential in each of the first clearing frames is larger than an absolute value of a clearing potential in each of the second clearing frames. Therefore, the emptying speed can be further increased based on the emptying frames with unequal emptying potentials, the signal acquisition period is shortened, and the imaging speed of the image sensor is improved.

Drawings

FIG. 1 is a schematic diagram of a signal acquisition circuit of an image sensor;

fig. 2 is a schematic structural diagram of the pixel array 20 in the signal acquisition circuit shown in fig. 1;

fig. 3 is a schematic structural diagram of the pixel array 20 and the signal readout chip 30 in the signal acquisition circuit shown in fig. 1;

FIG. 4 is a timing diagram of the signal acquisition circuit of FIG. 1 during signal acquisition;

FIG. 5 is a timing diagram of scan line 22a of FIG. 4;

FIG. 6 is a flow chart of a first embodiment of a signal acquisition method of the image sensor of the present invention;

FIG. 7 is a schematic diagram of a signal acquisition circuit of an image sensor used in the embodiment of the signal acquisition method shown in FIG. 6;

FIG. 8 is a timing diagram illustrating an embodiment of a signal acquisition method of the image sensor shown in FIG. 6;

FIG. 9 is a timing diagram of a second embodiment of a signal acquisition method of an image sensor according to the present invention;

FIG. 10 is a schematic diagram of a signal acquisition circuit of an image sensor used in the embodiment of the signal acquisition method shown in FIG. 9;

FIG. 11 is a timing diagram of a signal acquisition method of the image sensor according to a third embodiment of the present invention;

FIG. 12 is a timing diagram of a fourth embodiment of a signal acquisition method of an image sensor according to the present invention;

fig. 13 is a schematic structural diagram of a signal acquisition circuit of an image sensor employed in the embodiment of the signal acquisition method shown in fig. 12.

Detailed Description

As is clear from the background art, the existing signal acquisition method needs to be improved in the method of performing the blanking process on the pixels.

The problems are analyzed by combining a signal acquisition method of an image sensor and a signal acquisition circuit thereof.

Referring to fig. 1 and 2, fig. 1 is a schematic diagram of a signal acquisition circuit of an image sensor, and fig. 2 is a schematic diagram of a structure of a pixel array 20 in the signal acquisition circuit shown in fig. 1.

As shown in fig. 1 and 2, the signal acquisition circuit of the image sensor includes a pixel array 20, a scan line control circuit 10, and a signal Readout chip 30(Readout IC, ROIC for short). The pixel array 20 has a plurality of data lines 21 and a plurality of scan lines 22, the data lines 21 and the scan lines 22 define grids arranged in an array, and the area where the grids are located corresponds to the pixels 23.

The pixel 23 includes a signal switching device 231 (hereinafter referred to as a switching device 231), and a light sensing device 232. The switching device 231 is generally a Thin Film Transistor (TFT) device, and is used for controlling the on and off of the light sensing device 232 and the corresponding data line 21. The light sensing device 232 is used to collect an externally input optical signal and convert it into an electrical signal, which is then stored in the corresponding pixel 23. In fig. 2, each pixel 23 includes a switching device 231 and a photo sensing device 232 as an example.

Specifically, the photosensitive device 232 is a photodiode. The photodiode comprises a PIN junction amorphous silicon photodiode, a PN junction amorphous silicon photodiode, a PIN junction low-temperature polycrystalline silicon photodiode, a PN junction low-temperature polycrystalline silicon photodiode, a PIN junction organic matter photodiode, or a PN junction organic matter photodiode.

As shown in fig. 2, in each pixel 23, one end of the photosensitive device 232 is connected to the source (or drain) of the switching device 231, and the other ends of the photosensitive devices 232 are commonly connected to a common electrode 27 for applying a bias voltage; the control terminal of the switching device 231 in the pixels 23 in the same row is connected to a scan line 22, and the drain (or source) of the switching device 231 in the pixels 23 in the same column is connected to a data line 21.

When signal acquisition is performed, the scan line 22 is controlled by a peripheral driving circuit, such as the scan line control circuit 10, to realize the row-by-row opening of the switching devices 231, and the signal readout chip 30 reads out signals of the pixels 23 in the opened row in each column; when the switching device 231 is turned on under the control of the coupled scan line 22, a reverse bias is applied to the photo sensing device 232 through the common electrode 27; the electrical signal in the photosensitive device 232 in the reverse bias state can be conducted to the coupled data line 21, and then transmitted to the signal readout chip 30 through the data line 21 to realize signal acquisition.

Referring to fig. 3 in combination, fig. 3 is a schematic structural diagram of the pixel array 20 and the signal readout chip 30 in the signal acquisition circuit shown in fig. 1.

As shown in fig. 3, the signal readout chip 30 includes data processing channels 31 connected to the respective data lines 21, i.e., each data line 21 is connected to a corresponding data processing channel 31. Each data processing channel 31 includes a charge amplifier 311 and a filter circuit 312. The pixel charge enters the charge amplifier 311 through the data line 22 for amplification, then the noise is filtered by the filter circuit 312, and finally the analog-digital conversion is performed by the ADC circuit 32, wherein the ADC circuit 32 is commonly shared by a plurality of data channels. In some cases, in order to shorten the conversion time of the ADC, each data channel may be connected to a respective one of the ADC circuits 32.

In the charge amplifier 311, the potential a of the end connected to the data line 21 can be considered to be equal to the potential V0 of the reference potential end, so the potential of the data line 21 is always kept at V0.

Reference is now made in conjunction with fig. 4, wherein fig. 4 is a timing diagram of the signal acquisition circuit of fig. 1 during signal acquisition.

It should be noted that the timing chart shown in fig. 4 includes the driving timing of the scanning lines 22 and the driving timing of the signal readout chip 30, wherein each scanning line 22 (the scanning line 22c shown in fig. 3 is not shown in fig. 2) controls the pixel array 20 to be turned on row by row according to the timing shown in fig. 4.

The drive time of the scanning line 22a precedes the drive time of the scanning line 22b, and the drive time of the scanning line 22b precedes the drive time of the scanning line 22 c. And the signal readout chip 30 performs signal acquisition on a row-by-row basis. Each channel of the signal read-out chip 30 is connected to the data line 21, so that the potential value of each data line 21 is set by the signal read-out chip 30. The potential value of the common electrode 27 in fig. 4 is the potential value applied to the common electrode 27 in fig. 2 or fig. 3. When each pixel is turned on, the difference between the potential value of the common electrode 27 and the potential value of each data line 21 determines the value of the upper bias voltage applied to each light sensing device 232.

As shown in fig. 2 and 3, in a general application, the anodes of the light sensing devices 232 are connected to the common electrode 27, and the cathodes of the light sensing devices 232 are respectively connected to the switching devices 231. When each row of pixels is turned on, a positive voltage, that is, a forward bias voltage is applied to the light sensing device 232 by making the potential value of the common electrode 27 higher than that of each data line 21; when the pixels of each row are turned on, a negative voltage, i.e., in a reverse bias, is applied to the light sensing device 232 by making the potential value of the common electrode 27 lower than that of each data line 21.

In a general design, in order to simplify the chip design and reduce circuit noise, the potential of each input channel of the signal readout chip 30 is at a fixed value, and therefore the potential of the data line 21 is at a fixed value. It is necessary to determine the bias voltage value to which the photo-sensing device 232 is applied in each pixel by setting the potential value of the common electrode 27. That is, the bias voltage of the light sensing device 232 is equal to the potential value of the common electrode 27 — the potential value of the data line 21.

In practical applications, due to the leakage of the photodiode (dark current) and the incidence of ambient light, each pixel 23 (e.g., in the light-sensing device 232 and on the electrodes) has useless charges when the image sensor is used to capture an image. Thus, it is necessary to perform a blanking process for each pixel 23 before each signal acquisition.

Each signal acquisition cycle includes: at least one clear frame and a signal readout frame. The timing sequence of the clear frame and the signal readout frame is identical, and the clear frame and the signal readout frame are distinguished in that: in the blanking frame, after the signal of each pixel 23 is read out, the data is directly discarded without being retained. The remaining signals of the pixels 23 are thus read out by opening the blanking frame row by row, enabling blanking.

The interval of time that each row of pixels 23 is turned on in the blanking frame and the signal readout frame is the exposure time of each row of pixels 23. It can be seen that the start and end points of the exposure time for each row of pixels 23 are different, but the length of time is the same.

Referring collectively to fig. 5, fig. 5 is a timing diagram of scan line 22 of fig. 4. It should be noted that one pulse of the scan line represents scanning of one frame, that is, one pulse on the scan line in fig. 5 represents a sum of one pulse per scan line of a plurality of scan lines, such as

scan lines

22a, 22b, 22c … in fig. 4, so as to realize sequential row-by-row opening of pixels 23 in the pixel array 20 shown in fig. 2. However, if there are more signals left in the pixel 23, the photosensitive device 232 is in a saturated state, and fig. 5 takes the scan line 22a as an example, it needs to clear frames of a plurality of consecutive frames to discharge the charges in the row of photosensitive devices 232 coupled with the scan line 22a, and then starts the real sampling operation in the signal readout frame.

In practical use, the intensity of the ambient light of the environment where the image sensor is located cannot be determined. The number of the specific frames of the blanking frame cannot be determined, and it is not ensured that the signal in each pixel 23 can be completely blanked.

If the number of empty frames is set to be small, the residual signal in the pixel 23 is not determined. Specifically, if the ambient light is strong, the charge in the light-sensing device 232 is much left, and if the ambient light is weak, the charge in the light-sensing device 232 is little left.

More seriously, before the acquisition is started, if some pixels 23 are irradiated by strong light, the signal remains much, and some pixels 23 are irradiated by weak light, the signal remains less. In this case, if the number of empty frames is set to be small, the residual signal of each pixel 23 is not uniform, and the final image effect is seriously affected.

Therefore, in order to ensure that the signal in the pixel 23 can be cleared regardless of the intensity of the ambient light, it is necessary to use as many clearing frames as possible, for example, 50 frames, in one signal acquisition period, so as to ensure that the charge in the photo-sensing device 232 can be cleared as much as possible or the residual charge is less at any time (regardless of the intensity of the ambient light or the intensity of the ambient light).

Therefore, the adoption of the emptying mode of increasing the frame number of the emptying frame is a reason for the overall longer acquisition period of the existing signal acquisition method.

On the other hand, as described above, in the conventional signal pickup circuit, by controlling the potential of the common electrode 27, a positive bias or a negative bias is applied to the photosensitive device of the pixel to be picked up. However, as shown in fig. 2 and fig. 3, in the whole pixel array 20, one end of the photosensitive device 232 in all the pixels 23 is connected to one common electrode 27, that is, the common electrode 27 is connected to the photosensitive device 232 in all the pixels, the capacitance load connected to the common electrode 27 is large, and the capacitance load is charged or discharged by the common electrode 27 when the applied bias voltage value is changed by controlling the change of the potential of the common electrode 27; therefore, when the capacitive load of the common electrode 27 is large, the time required for charging and discharging the capacitive load of the common electrode 27 is quite long, which is another reason that the signal acquisition speed of the conventional signal acquisition method is too slow.

In order to solve the technical problem, the present invention provides a signal acquisition method of an image sensor, wherein the image sensor comprises: a plurality of pixels arranged in an array, a plurality of data lines and a plurality of scan lines, each of the pixels including a light sensing device and a signal switching device, one end of each of the light sensing devices being coupled to one of the data lines through the signal switching device, each of the pixels being connected to one of the scan lines through the signal switching device, the scan lines being adapted to turn on the signal switching devices of the connected pixels line by line, the signal acquisition method comprising: in each signal acquisition period, controlling the potential of the data line to be a target potential so as to apply bias voltage to the photosensitive device of each pixel which is turned on; the signal acquisition period comprises at least one reset frame, and the target potential is a reset potential during the reset frame so as to apply forward bias to the photosensitive device.

In the technical scheme of the invention, all pixels are closed when the potential of the data line is controlled to be the target potential, so that when the potential of the data line is changed, the capacitance load of the data line is only the parasitic capacitance of the data line, when the potential of the data line is changed, the capacitance load of the data line is smaller, the charge impact is small, the stabilization time required for changing the potential of the data line is short, the potential change speed of the data line is high, and the reset speed can be effectively improved; and during the reset frame is carried out, forward bias is applied to the photosensitive devices, the method can be equivalent to the method of irradiating each photosensitive device with strong light, the initial states of the photosensitive devices are adjusted to be consistent through the reset frame, and the influence of historical illumination, ambient light and the device difference of each photosensitive device on residual charges is eliminated.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

Referring to fig. 6 to 8, wherein fig. 6 shows a flow chart of a first embodiment of a signal acquisition method of the image sensor of the present invention; FIG. 7 is a schematic diagram of a signal acquisition circuit of an image sensor used in the embodiment of the signal acquisition method shown in FIG. 6; FIG. 8 is a timing diagram illustrating an embodiment of a signal acquisition method of the image sensor shown in FIG. 6.

As shown in fig. 7, the image sensor includes: a plurality of pixels 123, a plurality of data lines 121, and a plurality of scan lines 122 arranged in an array, each of the pixels 123 includes a signal switching device 1231 and a photo sensing device 1232, one end of each of the photo sensing devices 1232 is coupled to one of the data lines 121 through the corresponding signal switching device 1231, the signal switching device 1231 of each of the pixels 123 is connected to one of the scan lines 122, and the scan line 122 is adapted to turn on the signal switching devices 1231 of the connected pixels 123 row by row.

Specifically, the light sensing device 1232 is used to collect an externally input optical signal and convert the optical signal into an electrical signal, and then store the electrical signal in the corresponding pixel 123. Specifically, the light sensing device 1232 is a photodiode. The photodiode comprises a PIN junction amorphous silicon photodiode, a PN junction amorphous silicon photodiode, a PIN junction low-temperature polycrystalline silicon photodiode, a PN junction low-temperature polycrystalline silicon photodiode, a PIN junction organic matter photodiode, or a PN junction organic matter photodiode.

One end of the light sensing device 1232 is connected to the signal switching device 1231. The signal switching device 1231 is adapted to control the derivation of signal data within the pixel 123. The signal switching device 1231 is generally a Thin Film Transistor (TFT) device.

The signal switching device 1231 includes one end and the other end that can be conducted to each other and a control end that controls conduction and cut-off between the two ends, wherein, in the two ends that the signal switching device 1231 can be conducted to each other, one end with the photosensitive device 1232 is coupled, and the other end with the data line 121 is coupled, thereby realizing coupling between the photosensitive device 1232 and the data line 121.

In the plurality of pixels 123 arranged in an array, each column of the pixels 123 is coupled to the same data line 121; that is, the other ends of the signal switching devices 1231 in the pixels 123 of the same column are coupled to the same data line 121.

In the plurality of pixels 123 arranged in an array, each row of the pixels 123 is coupled to the same scan line 122; that is, the control terminals of the signal switching devices 1231 in the pixels 123 of the same row are coupled to the same scan line 122.

The signal acquisition circuit further comprises: a scan line control unit (not shown in the drawings), coupled to the plurality of scan lines 122, for controlling, by the scan lines 122, the signal switching devices 1231 of the pixels 123 connected to the scan lines 121 to be turned on line by line in each signal acquisition period; a signal readout unit 130, wherein the signal readout unit 130 is coupled to the data lines 121, and during each signal acquisition cycle, the signal readout unit reads the electrical signals of the turned-on pixels 123 through the data lines 122.

The signal readout unit 130 includes a plurality of data processing channels 131, and each data processing channel 131 includes a charge amplifier 1311 and a filter circuit (not shown). The electrical signal stored in the pixel 123 is transmitted to the signal readout unit 130, then enters a charge amplifier for amplification, then is filtered by a filter circuit to remove noise, and finally is subjected to analog-to-digital conversion by an ADC circuit, wherein the ADC circuit is generally shared by a plurality of data channels. Note that, in some cases, in order to shorten the conversion time of the ADC, a separate ADC circuit 32 may be connected to each data channel, which is not limited in the present invention.

When signal acquisition is performed, the scanning line control unit enables the signal switching devices 1231 to be turned on row by row, and the signal readout unit 130 reads out signals of the turned-on pixels 123 in each column; when the signal switching device 1231 is turned on under the control of the coupled scan line 122, the electrical signal in the light sensing device 232 can be conducted to the coupled data line 121, and then transmitted to the signal readout unit 130 through the data line 121 to realize signal acquisition.

It should be noted that, as shown in fig. 7, the other end of each of the photosensitive devices 1232 is commonly coupled to a common electrode 127 for applying a bias voltage to the photosensitive device 1232. Specifically, in each signal acquisition period, the potential of the common electrode 127 is kept unchanged to simplify circuit design, improve the stability of the voltage of the common electrode 127, and reduce circuit noise.

As shown in fig. 6, 7 and 8, the signal acquisition method includes: step S101 is executed to control the potential of the data line 121 to a target potential in each signal collecting period, so as to apply a bias voltage to the photosensitive device 1232 of each of the turned-on pixels 123.

Specifically, the signal acquisition circuit includes a bias control unit 140, the bias control unit 140 is coupled to the data line 121, and the bias control unit 140 is adapted to control the potential of the data line 121 to a target potential in each signal acquisition period, so as to apply a bias to the photosensitive device 1232 of each of the pixels 123 that are turned on row by row.

In each signal acquisition period, signal acquisition is performed on the plurality of pixels 123, and the potential of the data line 121 is controlled to a target potential, so as to apply a bias voltage to the photosensitive device 1232 of each pixel 123 which is turned on row by row. Since all the pixels 123 are turned off when the potential of the data line 121 is controlled to the target potential, when the potential of the data line 121 is changed, the capacitive load of the data line 121 is only the parasitic capacitance of the data line 121, so that the capacitive load of the data line 121 is small when the potential of the data line 121 is changed, the charge impact is small, the stabilization time required for changing the potential of the data line 121 is short, and the potential change speed of the data line 121 is high, thereby effectively shortening the signal acquisition period and improving the image acquisition speed.

The signal acquisition period includes at least one reset frame, and during the reset frame, the target potential is a reset potential to apply a forward bias to the light sensing device 1232; that is, before the reset frame is performed, the potential of the data line 121 is controlled to the reset potential V1 to apply a forward bias to the photosensitive device 1232 of each of the pixels 123 that is turned on. The bias control unit 140 controls the potential of the data line 121 to the reset potential V1 to apply a forward bias to the photosensitive device 1232 before the reset frame is performed.

During the reset frame, forward bias is applied to the photosensitive devices 1232, which is equivalent to irradiating each photosensitive device with strong light, and the initial states of the photosensitive devices 1232 are adjusted to be consistent through the reset frame, so that the influence of historical illumination, ambient light and device differences of the photosensitive devices on residual charges is eliminated.

It should be noted that, in this embodiment, as shown in fig. 8, each signal acquisition period includes 2 reset frames for example. However, this is only an example, and in other embodiments of the present invention, each signal acquisition period may also include only 1 reset frame, or include more than 2 (3, 4, or 5, etc.) reset frames.

Specifically, as shown in fig. 6, in step S101, the step of controlling the potential of the data line 121 to be the target potential to apply the bias voltage to the photosensitive device 1232 of each of the turned-on pixels 123 includes: executing step S1011, controlling the other end of the data line 121 to be coupled to the target potential; step S1012 is performed, the signal switching devices 1231 of the pixels 123 are turned on row by row, and a bias voltage is applied to the photosensitive devices 1232 of the turned-on pixels 123 through the data lines 121.

Specifically, the step of controlling the potential of the data line 121 to a target potential to apply a bias voltage to the photosensitive device 1232 of each of the turned-on pixels 123 includes: controlling the other end of the data line 121 to be coupled to the reset potential V1; the pixels 123 are turned on row by row, and a forward bias is applied to the photosensitive devices 1232 of the turned-on pixels 123 through the data lines 121.

Therefore, the bias control unit 140 includes: a controller (not shown) having one end coupled to the data line 121 and the other end coupled to the target potential, the controller being adapted to control the connection and disconnection between the data line 121 and the target potential.

Specifically, as shown in fig. 7, the controller includes a plurality of data line switches S1, each data line switch S1 has one end coupled to one of the data lines 121 and the other end coupled to a reset potential V1, and the data line switch S1 is adapted to control the corresponding data line 121 to be turned on and off in response to the reset potential V1.

With continuing reference to fig. 6, in step S1011, the step of controlling the other end of the data line 121 to be coupled to the target potential includes: controlling the other ends of the plurality of data lines 121 to be coupled to the target potential one by one. Specifically, before performing a reset frame, the other ends of the data lines 121 are controlled to be coupled to the reset potential V1 one by one. As shown in fig. 7, the data line switches S1 in the controller are closed one by one to couple the other ends of the data lines 121 to the reset potential V1 one by one.

The way of controlling the data lines 121 to be coupled to the target potential one by one can effectively control the capacitive load connected to the bias control unit 140 when the coupling is conducted, and can effectively reduce the impact generated by each coupling conduction, thereby shortening the time required for voltage stabilization, being beneficial to shortening the time required for controlling the steps of the data line potential to the target potential, and being beneficial to shortening the signal acquisition period.

It should be noted that the way of controlling the other ends of the data lines 121 to be coupled to the target potential one by one is only an example, and in other embodiments of the present invention, the other ends of the data lines may also be controlled to be coupled to the target potential at the same time, that is, all the data lines in the signal acquisition circuit are controlled to be coupled to the target potential at the same time; or controlling the other ends of the plurality of data lines to be coupled to the target potential in groups.

Specifically, before a reset frame is performed, the other ends of the plurality of data lines are controlled to be simultaneously coupled to the reset potential, that is, the plurality of data line switches in the controller are simultaneously closed so that the other ends of the plurality of data lines are simultaneously coupled to the reset potential; or, the other ends of the plurality of data lines are controlled to be coupled to the reset potential in groups, that is, the plurality of data line switches in the controller are closed in groups so that the other ends of the plurality of data lines are coupled to the reset potential in groups.

Wherein, controlling the other ends of the plurality of data lines to be coupled to the target potential in groups means that a plurality of data lines are grouped into one group, for example, every 2, 3 or 4 data lines are grouped into one group; the data lines in different groups are sequentially coupled to the target potential, and the data lines in the same group are simultaneously coupled to the target potential. Specifically, before the reset frame is performed, the data lines in the same group are simultaneously coupled to the reset potential, that is, the data line switches connected to the data lines in the same group are simultaneously closed to simultaneously couple the data lines in the same group to the reset potential. In addition, the number of data lines in different groups may be equal or unequal, so the data lines may be grouped according to the rule of 2, 3, 2 and 3 … ….

In addition, if the other end of the data line 121 is already in the coupled state before the reset frame is performed, but the coupled potential is a non-target potential, that is, although the other end of the data line is in the coupled state, the coupled potential is not the target potential corresponding to the reset frame, it is necessary to first release the coupled state. Therefore, as shown in fig. 6, before controlling the other end of the data line 121 to be coupled to the target potential, the step of controlling the potential of the data line 121 to be at the target potential to apply a bias voltage to the photosensitive device 1232 of each of the turned-on pixels 123 further includes: step S1010 is performed to disconnect the coupling of the data line and the non-target potential.

It should be noted that, in other embodiments of the present invention, before the reset frame is performed, when the other end of the data line 121 is not coupled to any circuit, the step S1010 may not be required to be performed.

In this embodiment, before the reset frame is performed, since the other end of the data line 121 is coupled to the corresponding data processing channel 131, step S1010 needs to be performed to disconnect the coupling of the data line and the non-target potential before controlling the other end of the data line 121 to be coupled to the target potential. Specifically, the step of disconnecting the coupling of the data line and the non-target potential includes: the coupling of the data lines 121 to the corresponding data processing channels 131 is interrupted.

Therefore, as shown in fig. 7, the bias control unit 140 further includes: a restorer (not shown) coupled to the data line 121 at one end and the signal readout unit 130 at the other end, the restorer being adapted to control the connection and disconnection of the data line 121 and the signal readout unit 130.

Specifically, the restorer includes a plurality of restoring switches S0, each restoring switch S0 is coupled to one of the data lines 121 at one end and to the corresponding data processing channel 131 of the connected data line 121 at the other end, and the restoring switch S0 is adapted to control the connection and disconnection of the data line 121 and the data processing channel 131.

In this embodiment, in step S1010, the step of disconnecting the coupling between the data line and the non-target potential includes: the coupling of the plurality of data lines 121 to the non-target potential is simultaneously cut off. Specifically, the coupling of the data lines 121 to the corresponding data processing channels 131 is simultaneously cut off, that is, all the data lines 121 in the signal processing circuit are simultaneously cut off from the coupling to the corresponding data processing channels 131. Specifically, as shown in fig. 7, the reset switches S0 in the restorer are simultaneously turned off to simultaneously turn off the coupling between all the data lines 121 and the corresponding data processing channels 131.

Because the circuit is not impacted by the coupling truncation or the impact is relatively small, the voltage stabilization time is not needed for the circuit coupling truncation, or the voltage stabilization time is very short, so that the simultaneous truncation of the coupling of the data lines 121 and the non-target potential can effectively improve the reset speed and shorten the duration of a signal acquisition period.

It should be noted that, the way of simultaneously disconnecting the coupling of the plurality of data lines 121 with the non-target potential is only an example, and in other embodiments of the present invention, the coupling of the plurality of data lines with the non-target potential may be disconnected one by one, that is, in some embodiments of the present invention, the coupling of the plurality of data lines with the corresponding data processing channels is disconnected one by one, and the plurality of reset switches in the restorer are disconnected one by one to disconnect the coupling of the plurality of data lines with the corresponding data processing channels; alternatively, the coupling groups of the plurality of data lines and the non-target potential are cut off, that is, in some embodiments of the present invention, the coupling groups of the plurality of data lines and the corresponding data processing channels are cut off, that is, the plurality of reset switch groups in the restorer are cut off to cut off the coupling groups of the plurality of data lines and the corresponding data processing channels.

The blocking of the coupling groups of the data lines and the corresponding data processing channels means that a plurality of data lines are grouped into one group, for example, every 2, 3 or 4 data lines are grouped into one group. The data lines in different groups and the corresponding data processing channels are sequentially cut off, and the data lines in the same group and the corresponding data processing channels are simultaneously cut off. That is, all reset switches connected to the data lines within the same group are simultaneously turned off to effect packet truncation in which the plurality of data lines are coupled to the corresponding data processing lanes. In addition, the number of data lines in different groups may be equal or unequal, so the data lines may be grouped according to the rule of 2, 3, 2 and 3 … ….

It should be noted that the controller can only control each data line 121 to be connected to one target potential or data processing channel 131 or not to be connected to any one target potential or data processing channel 131 at any time, so as to prevent a short circuit from occurring. That is, in the present embodiment, the controller 140 ensures that at most one of the data line switch S1 and the reset switch S0 is turned on for any one data line 121.

It should be further noted that, in this embodiment, the signal readout unit 130 and the bias control unit 140 are both integrated in the signal readout chip 340. However, this is merely an example, and in other embodiments of the present invention, the signal readout unit 130 and the bias control unit 140 may be separately disposed.

In addition, in the embodiment, for the same data line 121, after the coupling between the data line 121 and the corresponding data processing channel 130 is cut off, the other end of the data line 121 is controlled to be coupled to the target potential, that is, for the same data line 121, the other end of the data line 121 is controlled to be coupled to the target potential at any time after the coupling between the data processing channel 131 corresponding to the data line 121 is cut off.

Specifically, before performing the reset frame, after the same data line 121 is disconnected from the data line 121 and the corresponding data processing channel 131, the other end of the data line 121 is controlled to be coupled to the reset potential V1.

As shown in fig. 7, for the same data line 121, after the reset switch S0 in the restorer is turned off, the data line switch S1 in the controller is turned on again, so that the other end of the data line 121 is controlled to be coupled to the reset potential V1 after the coupling between the data line 121 and the corresponding data processing channel 131 is turned off.

Any time after the disconnection of the coupling between the data line 121 and the corresponding data processing channel 131 means that, for the same data line 121, as long as the coupling between the data line 121 and the corresponding data processing channel 131 is disconnected, the other end of the data line 121 can be controlled to be coupled to the target potential, regardless of whether the coupling between the other data line and the corresponding data processing channel 131 is disconnected.

Specifically, before the reset frame is performed, for the same data line 121, as long as the coupling between the data line 121 and the corresponding data processing channel 131 is cut off, the other end of the data line 121 can be controlled to be coupled to the reset potential V1, regardless of whether the coupling between the other data line 121 and the corresponding data processing channel 131 is cut off.

As shown in fig. 7, for the same data line 121, as long as the reset switch S0 corresponding to the data line 121 is turned off, the corresponding data line switch S1 may be closed regardless of whether the reset switch S0 corresponding to another data line 121 is turned off. That is, the opened and closed states of the plurality of data line switches S1 in the controller and the opened and closed states of the plurality of reset switches S0 in the restorer can be overlapped with each other with a misalignment.

Specifically, in this embodiment, the coupling between the data lines 121 and the corresponding data processing channels 131 is simultaneously cut off, and the other ends of the data lines 121 are controlled to be coupled to the reset potential V1 one by one; therefore, after the coupling between all the data lines 121 and the corresponding data processing channels 131 is cut off, the other ends of the data lines 121 are controlled to be coupled to the reset potential V1 one by one.

In other embodiments of the present invention, when the couplings of the data lines and the corresponding data processing channels are cut off one by one or in groups, after all the couplings of the data lines and the corresponding data processing channels are cut off, the other ends of the data lines are controlled to be coupled to the target potential one by one, simultaneously, or in groups; when the coupling of one part of the data lines and the corresponding data processing channel is cut off and the coupling of the other part of the data lines and the corresponding data processing channel is not cut off, the other ends of the cut off parts of the data lines are controlled to be coupled to the target potential one by one, or simultaneously, or in groups.

That is, in other embodiments of the present invention, when the plurality of reset switches are turned off one by one or in groups, after all the reset switches are turned off, the plurality of data line switches may be turned on one by one, simultaneously, or in groups; it is also possible to close the plurality of data line switches either individually, simultaneously, or in groups after a part of the reset switches are turned off.

With continued reference to fig. 6-8, the step of controlling the potential of the data line to the target potential to apply a bias voltage to the photosensitive device of each of the pixels that are turned on row-by-row further includes: in step S1012, the pixels 123 are turned on row by row, and a bias voltage is applied to the photosensitive devices 1232 of the turned-on pixels 123 through the data lines 121. Since the other end of the data line 121 is already coupled to the target potential, step S1012 is performed, and when the pixel 123 is turned on, a bias voltage can be applied to the photo sensing device 1232.

Therefore, the step of applying a bias to the photosensitive device 1232 of the turned-on pixel 123 during the reset frame proceeding includes: during the reset frame is in progress, the pixel 123 is turned on. Specifically, the pixel 123 is turned on by turning on the signal switching device 1231, and a forward bias is applied to the light sensing device 1232 of the turned-on pixel 123 through the data line 121. Specifically, as shown in fig. 8, in order to apply a forward bias to the photosensitive device 1232 of each of the pixels 123 that is turned on, the reset potential V1 is lower than the potential of the common electrode.

In this embodiment, after the other ends of the data lines 121 are all coupled to the target potential, the signal switching devices 1231 of the pixels 123 are turned on row by row, and a bias voltage is applied to the photosensitive devices 1232 of the turned-on pixels 123 through the data lines 121.

Therefore, before performing the reset frame, the plurality of data lines 121 are all disconnected from the corresponding data processing channels 131, and the other ends of the plurality of data lines 121 are all coupled to the reset potential V1; then, the reset frame is started, the pixel 123 is turned on, and a forward bias is applied to the photosensitive device 1232 of the turned-on pixel 123 through the data line 121.

As shown in fig. 7, before the reset frame is performed, all reset switches S0 in the restorer are turned off, and all data line switches S1 in the controller are closed; the reset frame is then started and the pixels 123 are turned on row by row to apply a forward bias to the photosensitive devices 1232 of the pixels 123 that are turned on.

Since all the data lines 121 are disconnected from the corresponding data processing channels 131, and the other ends of all the data lines 121 are coupled to the target potential, the potentials of the data lines 121 have stabilized at the target potential, and then the pixel 123 is turned on to apply a bias to the photosensitive device 1232 in the pixel 123.

As shown in fig. 7 and 8, in the plurality of pixels 123 arranged in an array, each row of the pixels 123 is coupled to the same scan line 122; that is, the control terminals of the signal switching devices 1231 in the pixels 123 of the same row are coupled to one scan line 122. Therefore, after all the data lines 121 are disconnected from the corresponding data processing channels 131 and the other ends of the data lines 121 are coupled to the target potential, the pixels 123 are turned on row by row, and a bias voltage is applied to the photosensitive devices 1232 of the turned-on pixels 123 through the data lines 121.

Specifically, before performing the reset frame, the plurality of data lines 121 are all disconnected from the corresponding data processing channels 131, and the other ends of the plurality of data lines 121 are all coupled to the reset potential V1; the reset frame is then started, the pixels 123 are turned on row by row, and a forward bias is applied to the photosensitive devices 1232 of the turned-on pixels 123 through the data lines 121.

With continuing reference to fig. 6-8, the signal acquisition cycle further comprises: a signal readout frame chronologically subsequent to the reset frame, the target potential being a readout potential V3 during the signal readout frame proceeding to apply a reverse bias to the photosensitive device 1232.

During the signal readout frame proceeding period, the scan line control unit turns on the plurality of pixels 123 line by line through the scan line 122; specifically, the scan line control unit turns on the pixels 123 by turning on the signal switching devices 1231 row by row. The data processing channel 131 of the signal readout unit 130 performs signal reading on the plurality of pixels 123 row by row through the corresponding data line 121, and stores the read signal values.

Therefore, the data line 121 is coupled to the data processing channel 131 before the signal read frame is performed. The potential of the data line 121 is equal to the reference potential V0. In the present embodiment, the readout potential V3 is equal to the reference potential V0.

As shown in fig. 7, before the signal readout frame is performed, all the reset switches S0 in the restorer are turned on, and all the data line switches S1 in the controller are turned off; the data readout frame is then started, and the pixels 123 are turned on row by row to apply a forward bias to the photosensitive devices 1232 of the turned-on pixels 123, thereby reading the signal values stored in the plurality of pixels 123 row by row.

In addition, as shown in fig. 8, in this embodiment, the signal acquisition cycle further includes: and an initialization frame which is located between the at least one reset frame and the signal readout frame and is adjacent to the signal readout frame in time sequence, wherein during the initialization frame, the data line is coupled with a data processing channel, and the target potential is a readout potential to apply a reverse bias to the photosensitive device.

During the initialization frame, the data line 121 is coupled to the data processing channel 131, the target potential is the readout potential V3, the photosensitive device 1232 is applied with a reverse bias voltage, so that the charge of each turned-on pixel 123 through the data processing channel 131 can be cleared, thereby implementing initialization of the pixel 123, and thus the cooperation of the reset frame and the initialization frame can improve the image acquisition accuracy of the image sensor, and ensure the consistency of the image acquired each time; in addition, by controlling the potential change of the data line 121 and applying forward bias or reverse bias, the capacitance load of the data line 121 is small, the potential change speed is high, the reset speed and the emptying speed can be effectively improved, the signal acquisition period can be shortened, and the imaging speed can be improved; in addition, the initialization frame and the signal readout frame are arranged adjacent in time sequence, so that the time period between the initialization frame and the signal readout frame is the time period for realizing signal integration of the image sensor, the connection relation of the data lines 121 is maintained stable from the initialization frame to the signal readout frame, unnecessary changes of the potentials of the data lines 121 are avoided, and circuit noise can be effectively suppressed.

Since the initialization frame is coupled to the data processing channel 131 as well as the data readout frame, the target potential during the initialization frame is the readout potential V3 as well as the signal readout frame, and in this embodiment, the potential of the data line 121 is equal to the reference potential V0, i.e., V3 is equal to V0.

Therefore, before performing the initialization frame, step S1011 is executed, and the step of controlling the other end of the data line 121 to be coupled to the target potential includes: controlling the other ends of the plurality of data lines 121 to be coupled to the readout potential V3 one by one before performing an initialization frame; then, the initialization frame is started, step S1012 is performed to turn on the pixels 123 row by row, and a reverse bias is applied to the photosensitive devices 1232 of the turned-on pixels 123 through the data lines 121.

As shown in fig. 7, before the initialization frame is performed, all the reset switches S0 in the restorer are closed, and all the data line switches S1 in the controller are turned off; the initialization frame then begins, turning on the pixels 123 on a row-by-row basis to apply a reverse bias to the photosensitive devices 1232 of the pixels 123 that are turned on. It can be seen that, in the time period from the initiation of the initialization frame to the end of the signal readout frame, the data processing channel 131 is used to apply the reverse bias voltage to the photosensitive device 1232, and any switch in the restorer and the controller does not need to be opened or closed, so that the circuit noise can be effectively suppressed.

In addition, in this embodiment, in the time domain, before the initialization frame is located after the reset frame, and therefore the other ends of the data lines 121 are controlled to be coupled to the data processing channel 131, the signal acquisition method further includes: the coupling of the data line 121 to the reset potential V1 is cut off. In this embodiment, the coupling of the data lines 121 and the reset potential V1 is simultaneously interrupted.

In this embodiment, before the initialization frame is started, the step of controlling the data line 121 to be coupled to the data processing channel, the step of disconnecting the coupling between the data line 121 and the reset potential V1, and the bias control unit 140 controlling the data line switch S1 to be disconnected and the reset switch S0 to be closed, may refer to the situation that before the at least one reset frame is started, the data line 121 is coupled, and the bias control unit 140 controls the reset switch S0 to be disconnected and the data line switch S1 to be closed, that is, the reset switch S0 is disconnected, or the data line switches are turned on simultaneously, one by one, or in groups; the present invention will not be described herein.

In addition, it should be noted that, in the initialization frame, the signal values stored in the plurality of pixels 123 are discarded.

Referring to fig. 9 and 10, fig. 9 is a timing chart of a second embodiment of the signal acquisition method of the image sensor of the present invention, and fig. 10 is a schematic structural diagram of a signal acquisition circuit of the image sensor employed in the embodiment of the signal acquisition method shown in fig. 9.

The present embodiment is the same as the previous embodiments, and the description of the present invention is omitted. The present embodiment is different from the previous embodiment in that the signal acquisition period further includes: at least one clearing frame, which is located between the at least one reset frame and the initialization frame in time sequence, and during the clear frame, the target potential is a clearing potential V2 to apply a reverse bias to the photosensitive device 2231, that is, before the clear frame is performed, the potential of the data line 221 is controlled to the clearing potential to apply the reverse bias to the photosensitive device 2232 of each of the pixels 223 that is turned on.

Specifically, before the blanking frame is performed, the potential of the data line 221 is controlled to the blanking potential V2, so as to apply a reverse bias to the photosensitive device 2232 of each of the pixels 223 that are turned on row by row. The bias control unit 240 controls the potential of the data line 221 to the clear potential V2 to apply a reverse bias to the photosensitive device 2232 before the clear frame is performed.

Ensuring that the charge in each photosensitive device 2232 can be effectively cleared by the clearing frame; and by controlling the potential change of the data line 221 and applying forward bias or reverse bias, the capacitance load of the data line 221 is small, the potential change speed is high, the reset speed and the emptying speed can be effectively improved, the signal acquisition period can be shortened, and the imaging speed can be improved.

Specifically, in order to apply a reverse bias to the photosensitive device 2232 of each of the pixels 223 that are turned on, in this embodiment, the clear potential V2 is higher than the potential of the common electrode; moreover, as shown in fig. 9, in the present embodiment, the absolute value of the clear potential V2 is greater than the absolute value of the readout potential V3, so that the photosensitive device 2232 applies a larger reverse bias voltage under which the signal in each pixel is cleared more quickly, thereby enabling an effective reduction in image reading speed.

It should be noted that, as shown in fig. 9, in this embodiment, it is described by taking an example that each signal acquisition period includes 1 reset frame and 1 clear frame. However, this is only an example, and in other embodiments of the present invention, each signal acquisition period may also include only 2 or more (3, 4, or 5, etc.) reset frames, or 2 or more (3, 4, or 5, etc.) clear frames.

In order to realize the switching of the data lines at different target potentials, referring to fig. 10 in combination, the bias control unit 240 further includes: a converter (not shown) adapted to effect a conversion of the coupling of the other end of the controller (not shown) between different target potentials.

Specifically, as shown in fig. 10, the converter includes: a first switch S11, one end of the first switch S11 being coupled to the other end of the controller, the other end of the first switch S11 being coupled to the reset potential V1, the first switch S11 being adapted to control the connection and disconnection of the other end of the controller coupled to the reset potential V1; at least one second switch S12, one end of each second switch S12 is coupled to the other end of the controller, the other end of each second switch S12 is coupled to a clearing potential V2, and each second switch S12 is adapted to control the connection and disconnection of the other end of the controller coupled to a clearing potential V2.

Therefore, before performing the blanking frame, the other ends of the plurality of data lines 221 are controlled to be coupled to the blanking potential V2 one by one; then, the clear frame is started, the pixel 223 is turned on, and a reverse bias voltage is applied to the photosensitive device 2232 of the turned on pixel 223 through the data line 221.

Furthermore, since the at least one clearing frame is located after the at least one reset frame in terms of time sequence, in this embodiment, before the clearing frame is performed, before the other ends of the plurality of data lines 221 are controlled to be coupled to the clearing potential V2 one by one, the signal acquisition method further includes: the coupling of the data line 121 to the reset potential V1 is cut off. In this embodiment, the coupling of the data lines 221 and the reset potential V1 is simultaneously interrupted.

Specifically, before the blanking frame is performed, all reset switches S0 in the restorer are turned off, all data line switches S12 in the controller are turned off, a first switch S1 in the converter is turned off, and all second switches S12 in the converter are turned on; then, the clear frame is started, the pixels 223 are turned on row by row, and a reverse bias voltage is applied to the photosensitive devices 2232 of the turned-on pixels 223 through the data lines 221.

In this embodiment, before the at least one clearing frame is started, the step of controlling the data line 221 to be coupled to the clearing potential V2 and the step of disconnecting the data line 221 from the reset potential V1 may be performed by the bias control unit 240 controlling the data line switch S1 to be turned on, the reset switch S0 to be closed, the first transfer switch S11 to be turned off, the second transfer switch S12 to be closed, and the like. The present invention will not be described herein.

It is further noted that, within each of the blanking frames, the signal values stored by the plurality of pixels 223 are discarded.

In addition, in the present embodiment, the fact that the absolute value of the clear potential V2 is larger than the absolute value of the readout potential V3 is merely an example.

Referring to fig. 11, fig. 11 is a timing chart of a signal acquisition method of the image sensor according to the third embodiment of the present invention. In the embodiment shown in fig. 11, the absolute value of the clear potential V2 may also be equal to the absolute value of the sense potential V3.

It should be noted that, in this embodiment, the signal acquisition circuit shown in fig. 10 may be used to realize signal acquisition, that is, in fig. 10, although the clear potential V2 and the readout potential V3 are two power supplies, the absolute value of the clear potential V2 is equal to the absolute value of the readout potential V3.

Referring to fig. 12 and 13, fig. 12 is a timing chart of a fourth embodiment of the signal acquisition method of the image sensor of the present invention, and fig. 13 is a schematic structural diagram of a signal acquisition circuit of the image sensor employed in the embodiment of the signal acquisition method shown in fig. 12.

The present embodiment is the same as the previous embodiments, and the description of the present invention is omitted. The difference between this embodiment and the foregoing embodiment is that, in the same signal acquisition period, the blanking potentials in different blanking frames are not equal.

It should be noted that, in the same signal acquisition period, different blanking frames in which the blanking potentials are not equal are merely an example. In other embodiments of the present invention, in the same signal acquisition period, the blanking potentials may also be equal in different blanking frames.

Specifically, as shown in fig. 12, the at least one clearing frame includes at least one first clearing frame and at least one second clearing frame, and an absolute value of a clearing potential during the first clearing frame is larger than an absolute value of a clearing potential during the second clearing frame.

It should be noted that, as shown in fig. 12, in this embodiment, it is described by taking an example that each signal acquisition period includes 1 reset frame, 1 first clear frame, and 1 second clear frame. However, this is only an example, and in other embodiments of the present invention, each signal acquisition period may also include only 2 or more (3, 4, or 5, etc.) reset frames, or 2 or more (3, 4, or 5, etc.) first clear frames, or 2 or more (3, 4, or 5, etc.) second clear frames.

Since the absolute value of the clear potential during the first clear frame proceeding period is larger, the photosensitive device 3232 is applied with a larger reverse bias during the first clear frame proceeding period; under larger reverse bias, each pixel is emptied more quickly, so that the emptying speed can be increased, the signal acquisition period is shortened, and the imaging speed of the image sensor is improved. Specifically, the blanking potential V2 during each of the first blanking frame proceeding periods₁Absolute value of (2)For the blanking potential V2 during the execution of each of the second blanking frames₂1 to 3 times the absolute value of (a).

In this embodiment, in the same signal acquisition period, the at least one first clear frame is located before the at least one second clear frame in time sequence.

On the other hand, as shown in fig. 12, in the present embodiment, the minimum value of the absolute value of the clear potential V2 is equal to the absolute value of the readout potential V3; therefore, the blanking potential V2 during the first blanking frame is performed₁Is greater than the minimum of the absolute values of the clear potentials. Specifically, the blanking potential V2 during the second blanking frame is performed₂Is the minimum of the absolute values of the clearing potentials.

In order to simplify the circuit structure and reduce the number of power supplies, in this embodiment, the data lines 321 are coupled to the data processing channel 331 when the readout potential is the minimum of the absolute values of the clear potentials, that is, when the target potential is the clear potential with the minimum absolute value. I.e., the second clear frame, the initialization frame and the data read frame, are supplied with the target potential through the data processing path 331, so V2₁＝V3＝V0。

Therefore, as shown in fig. 13, the converter includes: a first switch S11, one end of the first switch S11 being coupled to the other end of the controller, the other end of the first switch S11 being coupled to the reset potential, the first switch S11 being adapted to control the connection and disconnection of the other end of the controller coupled to the reset potential V1; at least one second switch S12, one end of the second switch S12 being coupled to the other end of the controller, the other end of the second switch S12 being coupled to a blanking potential during a first blanking frame, the second switch S12 being adapted to control the connection and disconnection of the other end of the controller to the blanking potential during a first blanking frame.

In summary, in the signal acquisition method and the signal acquisition circuit provided by the present invention, in each signal acquisition period, signal acquisition is performed on the plurality of pixels, and the potential of the data line is controlled to the target potential, so as to apply a bias voltage to the photosensitive device of each of the pixels that is turned on. When the potential of the data line is changed, the load of the data line is only the parasitic capacitance of the data line, so that the load of the data line is small when the potential of the data line is changed, the charge impact is small, the stabilization time required by changing the potential of the data line is short, and the potential change speed of the data line is high, so that the signal acquisition period can be effectively shortened, and the image acquisition speed is improved; and each signal acquisition cycle comprises: the signal acquisition period comprises at least one reset frame, and during the reset frame, the target potential is a reset potential so as to apply forward bias to the photosensitive device; and during the reset frame, applying forward bias to the photosensitive devices, which can be equivalent to irradiating each photosensitive device with strong light, adjusting the initial state of each photosensitive device to be consistent through the reset frame, and eliminating the influence of historical illumination, ambient light and the device difference of each photosensitive device on residual charge. In an alternative aspect of the present invention, the signal acquisition period further includes: an initialization frame positioned between the at least one reset frame and the signal readout frame and adjacent to the signal readout frame, the data lines coupled to the data processing channels to apply a reverse bias to the photosensitive devices during the initialization frame. During the initialization frame, the data line is coupled with the data processing channel, and the photosensitive device is applied with reverse bias voltage, so that the charge of each turned-on pixel through the data processing channel can be cleared, and the initialization of the pixel is realized; in addition, the initialization frame and the signal reading frame are arranged adjacent in time sequence, and the connection relation of the data lines is not changed from the initialization frame to the signal reading frame, so that the circuit noise can be effectively inhibited. In an alternative aspect of the present invention, the signal acquisition period further includes at least one clear frame, and the target potential is a clear potential during the clear frame to apply a reverse bias to the photosensitive device. The charge in each photosensitive device can be effectively emptied by the emptying frame. Therefore, through the matching of the reset frame and the empty frame, the image acquisition precision of the image sensor can be improved, and the accuracy of the image acquired each time is ensured; and by controlling the potential change of the data line, forward bias or reverse bias is applied, the load of the data line is small, the potential change speed is high, the reset speed and the emptying speed can be effectively improved, the signal acquisition period can be shortened, and the imaging speed can be improved. In an alternative aspect of the invention, the at least one clearing frame includes at least one first clearing frame and at least one second clearing frame, wherein an absolute value of a clearing potential during the first clearing frame proceeding period is larger than an absolute value of a clearing potential during the second clearing frame proceeding period. Therefore, the emptying speed can be further increased based on the emptying frames with unequal emptying potentials, the signal acquisition period is shortened, and the imaging speed of the image sensor is improved.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A signal acquisition method of an image sensor, the image sensor comprising: a plurality of pixels arranged in an array, a plurality of data lines and a plurality of scan lines, each of the pixels including a light sensing device and a signal switching device, one end of each of the light sensing devices being coupled to one of the data lines through the signal switching device, each of the pixels being connected to one of the scan lines through the signal switching device, the scan lines being adapted to turn on the signal switching devices of the connected pixels line by line,

the signal acquisition method is characterized by comprising the following steps:

in each signal acquisition period, controlling the potential of the data line to be a target potential so as to apply bias voltage to the photosensitive device of each pixel which is turned on;

the signal acquisition period comprises at least one reset frame, and the target potential is a reset potential during the reset frame so as to apply forward bias to the photosensitive device.

2. The signal acquisition method according to claim 1, wherein the step of controlling the potential of the data line to a target potential to apply a bias voltage to the photosensitive device of each of the pixels that is turned on comprises:

controlling the other end of the data line to be coupled to the target potential;

the signal switching devices of the pixels are turned on row by row, and a bias voltage is applied to the light sensing devices of the turned-on pixels through the data lines.

3. The signal acquisition method according to claim 2, wherein the step of controlling the other end of the data line to be coupled to the target potential comprises:

controlling the other ends of the plurality of data lines to be coupled to the target potential one by one;

or controlling the other ends of the plurality of data lines to be coupled to the target potential at the same time;

or controlling the other ends of the plurality of data lines to be coupled to the target potential in groups.

4. The signal collection method of claim 2, wherein the step of controlling the potential of the data line to a target potential to bias the photosensitive device of each of the turned-on pixels before controlling the other end of the data line to be coupled to the target potential further comprises: the coupling of the data line to the non-target potential is cut off.

5. The signal acquisition method of claim 4, wherein the step of disabling the coupling of the data line to the non-target potential comprises:

cutting off the coupling of the plurality of data lines with the non-target potential one by one;

or, the coupling of the plurality of data lines with the non-target potential is simultaneously cut off;

alternatively, the coupling group of the plurality of data lines and the non-target potential is cut off.

6. The signal acquisition method according to claim 4, wherein, for the same data line, after the data line is disconnected from the coupling with the non-target potential, the other end of the data line is controlled to be coupled with the target potential.

7. The signal acquisition method according to any one of claims 2 to 6, wherein after the other ends of the plurality of data lines are all coupled to the target potential, the signal switching devices of the pixels are turned on line by line, and a bias voltage is applied to the photosensitive devices of the turned-on pixels through the data lines.

8. The signal acquisition method according to claim 1, wherein the signal switching devices of the pixels in each row are coupled to the same scanning line in the plurality of pixels arranged in an array.

9. The signal acquisition method of claim 1, wherein the signal acquisition cycle further comprises:

a signal readout frame chronologically positioned after the reset frame, during which the data line is coupled to a data processing channel, the target potential being a readout potential to apply a reverse bias to the photosensitive device.

10. The signal acquisition method of claim 9, wherein the signal acquisition cycle further comprises:

and an initialization frame which is located between the at least one reset frame and the signal readout frame and is adjacent to the signal readout frame in time sequence, wherein during the initialization frame, the data line is coupled with a data processing channel, and the target potential is a readout potential to apply a reverse bias to the photosensitive device.

11. The signal acquisition method of claim 10, wherein the signal acquisition cycle further comprises:

and at least one clear frame, which is located between the at least one reset frame and the initialization frame in time sequence, wherein during the clear frame, the target potential is a clear potential to apply a reverse bias to the photosensitive device.

12. The signal acquisition method according to claim 11, wherein the blanking potentials are equal or unequal in different blanking frames in the same signal acquisition period.

13. The signal acquisition method according to claim 12, wherein the at least one blanking frame includes at least one first blanking frame and at least one second blanking frame, and an absolute value of a blanking potential during the first blanking frame is larger than an absolute value of a blanking potential during the second blanking frame.

14. The signal acquisition method of claim 13, wherein the at least one first blanking frame temporally precedes the at least one second blanking frame in the same signal acquisition cycle.

15. The signal acquisition method according to claim 13, wherein an absolute value of the blanking potential during the first blanking frame proceeding is 1 to 3 times an absolute value of the blanking potential during the second blanking frame proceeding.

16. The signal acquisition method of claim 11, wherein an absolute value of the clearing potential is greater than or equal to an absolute value of the readout potential.

17. The signal acquisition method according to claim 1, wherein the other end of each of the photosensitive devices is coupled to a common electrode, and a potential of the common electrode is kept constant in each signal acquisition period.

18. A signal acquisition circuit of an image sensor, the image sensor comprising: a plurality of pixels arranged in an array, a plurality of data lines and a plurality of scan lines, each of the pixels including a light sensing device and a signal switching device, one end of each of the light sensing devices being coupled to one of the data lines through the signal switching device, each of the pixels being connected to one of the scan lines through the signal switching device, the scan lines being adapted to turn on the signal switching devices of the connected pixels;

the signal acquisition circuit includes:

the scanning line control unit is coupled with the plurality of scanning lines, and in each signal acquisition period, the scanning line control unit controls the signal switching devices of the pixels connected with the scanning lines to be turned on line by line through the scanning lines;

the signal readout unit is coupled with the data lines and reads the electric signals of the started pixels through the data lines in each signal acquisition period;

characterized in that, the signal acquisition circuit still includes:

a bias control unit coupled to the data lines, the bias control unit being adapted to control the potentials of the data lines to a target potential using the signal acquisition method according to any one of claims 1 to 17 in each signal acquisition period to apply a bias to the photosensitive devices of each of the pixels that are turned on line by line.

19. The signal acquisition circuit of claim 18, wherein the bias control unit comprises:

and one end of the controller is coupled with the data line, the other end of the controller is coupled with the target potential, and the controller is suitable for controlling the connection and disconnection between the data line and the target potential.

20. The signal acquisition circuit of claim 19 wherein the bias control unit further comprises:

and one end of the restorer is coupled with the data line, the other end of the restorer is coupled with the data processing channel, and the restorer is suitable for controlling the connection and disconnection of the data line and the data processing channel.

21. The signal acquisition circuit of claim 20, wherein the controller comprises a plurality of data line switches, each data line switch having one end coupled to one of the data lines and another end coupled to a target potential, the data line switch adapted to control the connection and disconnection of the corresponding data line coupled to the target potential;

the restorer comprises a plurality of restoring switches, one end of each restoring switch is coupled with one data line, the other end of each restoring switch is coupled with a data processing channel corresponding to the connected data line, and the restoring switches are suitable for controlling the connection and disconnection of the data lines and the data processing channels.

22. The signal acquisition circuit of claim 20 wherein the bias control unit further comprises: a converter adapted to effect conversion of the coupling of the other end of the controller between different target potentials.

23. The signal acquisition circuit of claim 22 wherein the signal acquisition cycle comprises:

at least one reset frame, during the reset frame, the target potential is a reset potential to apply a forward bias to the photosensitive device;

a signal readout frame chronologically positioned after the reset frame, during which the data line is coupled to a data processing channel, the target potential being a readout potential to apply a reverse bias to the photosensitive device;

an initialization frame positioned between and adjacent to the at least one reset frame and the signal readout frame in time sequence, during which the data lines are coupled to a data processing channel and the target potential is a readout potential to apply a reverse bias to the photosensitive device;

at least one clearing frame, wherein the clearing frame is positioned between the reset frame and the initialization frame in time sequence, and the target potential is a clearing potential during the clearing frame to apply a reverse bias voltage to the photosensitive device;

the converter includes:

a first transfer switch, one end of which is coupled to the other end of the controller, the other end of which is coupled to the reset potential, the first transfer switch being adapted to control the connection and disconnection of the other end of the controller coupled to the reset potential;

and each second change-over switch is suitable for controlling the connection and disconnection of the other end of the controller and one clearing potential.

24. The signal acquisition circuit of claim 22 wherein the signal acquisition cycle comprises:

the minimum value of the absolute value of the clear potential is equal to the absolute value of the readout potential;

the at least one clear frame includes at least one first clear frame during which an absolute value of a clear potential is greater than a minimum value of the absolute value of the clear potential; the converter includes:

at least one second transfer switch, one end of the second transfer switch being coupled to the other end of the controller, the other end of the second transfer switch being coupled to a blanking potential during a first blanking frame, the second transfer switch being adapted to control the turning on and off of the coupling of the other end of the controller to a blanking potential during a first blanking frame.